Automated flexible assembly systems (FAS) are capable of being programmed to assemble several different products on a single assembly line with minimal equipment changes. For manufacturers who produce several different products in volumes too small to justify the expense of having a separate assembly line for each product, FASs are more economical than traditional manual or dedicated automated production methods. FASs allow a manufacturer to produce several different products in limited volumes with essentially the same amount of equipment that would be necessary to produce a single product in high production volumes. Flexible assembly systems are also advantageous over dedicated automated systems because when a product is updated or redesigned, a FAS typically can be modified to produce the new, redesigned product with minimal or no equipment changes.
In accordance with the above described characteristics, FASs require parts feeding systems which can feed a variety of different parts on command in proper orientation, position and spacing to the part manipulator (such as a robotic arm or machine tool). The most common type of flexible parts feeder is the vibratory bowl feeder. A vibratory bowl feeder comprises a cylindrical container with a spiral track or groove extending from the floor of the container to the top rim. The entire assembly is motivated by a helical vibration which tends to convey the parts up the spiral track. Disposed along the path of the spiral track are one or more guides, for example, a height bar, which tend to orient the part in the desired orientation or, if the part cannot be properly oriented, will not let the part continue up the track. A part which cannot pass through the guide will eventually fall from the track back to the bottom of the cylindrical container and start its way back up the track again, possibly in an orientation which can pass through the guide or guides. Conventional bowl feeders must be custom tooled to a single part, or a small number of parts which are substantially identical in size and shape and are, therefore, inappropriate for FAS use.
Flexible parts feeding systems have been developed for FASs utilizing the bowl feeder type of system. Such systems are described, for instance, in Maul G. P., Goodrich, J. L., A Methodology for Developing Programmable Parts Feeders, IIE Trans., v. 15, no. 4, 1983, and Suzuki, T., Kohno, M., The Flexible Parts Feeder Which Helps A Robot Assemble Automatically, Assembly Automation, v.1, no. 2, 1981.
Other flexible parts feeding systems have been designed using conveyor belts or linear vibratory tracks rather than the spiral shaped tracks found in bowl feeders. Zenger, D., Dewhurst, P., Automatic Handling Of Parts For Robot Assembly, Annals of CIRP, v. 33, no. 1, 184 and Cowart N. A., et al., Programmable Assembly Research, Technology Transfer To Industry-Phase II, Westinghouse R & D Center, ISP 78-18773, Pittsburgh 1981, describe systems which use simple interchangeable mechanisms to customize a conveyor to reject parts not in a particular orientation. In these systems, an optical sensor is mounted at the end of a conveyor and checks the orientation of each part as it passes under the sensor by comparing its optical signature with a sample signature stored in memory. Some of these types of systems use linear vibration to urge the parts along the track in the desired direction.
U.S. Pat. No. 4,909,376, issued to Herndon et al., discloses an automated parts feeding mechanism which utilizes visual monitoring to determine the location and orientation of parts. In this device, a feed plate having multiple parts thereon is vibrated to urge the parts along its top surface and a counter rotating brush is positioned above the vibrating plate to help separate the parts. The parts are transported to a viewing section where a camera takes a video image of each part. The image is computer analyzed to determine the location and orientation of the part. If the part is appropriately positioned and oriented a manipulator is controlled to pick up the part whereupon the part can be assembled to the product or further worked on.
It is an object of the present invention to provide an improved parts feeding system for a flexible assembly system.
It is another object of the present invention to provide an automatically reconfigurable parts feeding system that can be adapted to feed parts of a wide variety of shapes and sizes.
It is another object of the present invention to provide an automatically reconfigurable parts feeding system that can be adapted to feed parts of a wide variety of shapes and sizes without the need for manual intervention or changing of parts of the feeding system.
It is a further object of the present invention to provide a parts feeding system which can rapidly change the parts being fed through the system.
It is yet another object of the present invention to provide a parts feeding system which utilizes vision based parts inspection to improve reliability.
It is yet another object of the present invention to provide a parts feeding system which requires a minimal amount of hardware.
It is yet another object of the present invention to provide a parts feeding system having vision based part orientation determination which simultaneously obtains two different views of the part.
It is one more object of the present invention to provide a vision based parts feeding system which can be programmed to measure a region of interest in one view based on information obtained from another view.